Heating furnaces

ABSTRACT

A furnace having sidewalls, end walls, a top wall and a bottom wall defining a heating chamber in which material to be heated enters the heating chamber through one of the end walls and exits through the other of the end walls. A plurality of burner stations are spaced along at least one of the sidewalls. Exhaust port means for each burner station are formed in a wall above its associated burner station whereby a flow pattern for substantially the combustion products of each burner station is established from each burner station out in a first current over material in the heating chamber and up and back over the first current in a second current to the exhaust port means above that burner station. Recuperator means are provided for each exhaust port means for passing combustion products from the exhaust port means in heat exchange relationship with combustion air for the burner stations to preheat the combustion air.

[72] Inventor Magnus L. Froberg 3,476,368 11/1969 Saiki 263/20 pp No 2322" ohm Primary Examiner.lohn J. Camby Filed p 1970 AttorneyStael|n &Overman [45] Patented Jan. 11, 1972 Assignee owens'col'ning Fiberglascorlml'aflon ABSTRACT: A furnace having sidewalls, end walls, a top walland a bottom wall defining a heating chamber in which material to beheated enters the heating chamber through one of the [54] i f i fg endWalls and exits through the other of the end walls. A plualms rawmgrality of burner stations are spaced along at least one of the [52] US.Cl 263/15 R, sidewalls. Exhaust port means for each burner station are263/20 formed in a wall above its associated burner station whereby a[51] Int. Cl F231 15/04 fiow pattern for substantially the combustionproducts ofeach [50] Field of Search 263/20, 15 burner station isestablished from each burner station out in a R first current overmaterial in the heating chamber and up and back over the first currentin a second current to the exhaust [56] References C'ted port meansabove that burner station. Recuperator means are UNITED STATES PATENTSprovided for each exhaust port means for passing combustion 1,66L336 92Kutchka et a1 263/]5 products from the exhaust port means in heatexchange relationship with combustion air for the burner stations topreheat the combustion air.

. COMMON STACK 7! AIR SUPPLY FUEL SUPPLY PATENTEU JAN SHEET 1 OF 2 7 (1i T 50 992 FUEL 12 1 g FUEL SUPPLY {p SUPPLY 19 Fig-i INVENTOR.

mam/s A. FROBR6 BY $462M PATENTEBJANHEYZ 31633886 SHEEI 2 OF 2 INVETJTOR.

jM/vz/s L FROBIFRG HEATING FURNACES This invention relates to heatingfurnaces in general and particularly to such furnaces which utilizerecuperators wherein the combustion products from the burner stationsare used to preheat combustion air which is to be mixed with the fuel ata burner station.

The invention will be disclosed and discussed herein in connection withheating furnaces such as those used in the glass industry, in which flueor exhaust gases are used to preheat combustion air for the furnaceburners, although it will be apparent that the invention will have otheruses and provide advantages in other types of furnaces.

ln glass industry heating furnaces, it is necessary to burn substantialamounts of fuel with large volumes of air in order to achieve hightemperatures and the large quantities of heat required for glass-meltingoperations. This results in large volumes of waste and flue gases,having high temperatures and heat content remaining after the primaryheating use. These factors have long made itadvantageous to userecuperators or regenerators to recover some of the heat of the wastegases by using the hot flue gases to preheat the combustion air and thusincrease the output of the furnace for a given amount of fuelconsumption.

In recent years the greatly increased cost of fuel, labor and capitalequipment and the attendant necessity for close cost control in allglass-making operations, have made it important to recover as much heatas possible from the flue gases and transfer it to the incomingcombustion air in order to increase the heating efficiency and thus theoutput of the furnace to the greatest extent possible. It is alsoimportant that furnace shutdowns for maintenance, such as repair orreplacement of recuperators, be reduced to a minimum. While new furnaceinstallations are designed and built with these factors in mind, greatefforts are also .being made to increase the efficiencies and outputs ofexisting furnaces because of the high cost of new furnaces and longtimes required to build and put them into operation; an increasedrecovery of otherwise wasted heat and flue gases being one of the mosteffective and economical approaches toward achieving increases inefficiency and output of old furnaces.

For these reasons, if recuperators are employed it is desirable to notonly provide high recovery of heat from flue gases, but also to providea long service life with a minimum of maintenance and shutdown. This,however, is exceedingly difficult to achieve because of the extremelyrigorous service conditions to which recuperator heat exchange elementsare subjected in operation. Recuperator-type heat exchangers aredesirable since the flame direction and combustion gas flow in onedirection enables better and more uniform control of the temperature ofthe preheated combustion air. There is no interruption of firing, as ina regenerator type furnace, further enabling closer control over thefurnace temperature. Substantially uniform flame temperatures in arecuperator-type furnace helps preserve the refractory on the interiorof the heating chamber. Further, in most recuperator-type installationsthere is no clogging of checker work in stack or exhaust passages asfound in regenerator-type installations.

On the other hand, regenerators are particularly useful with largefurnaces since in the past the use of single or even dualrecuperatorinstallations would have required recuperators that were too large toservice the larger furnaces. Additionally, better control of the flamepatterns is achieved since the flame leaves a burner station and isdirected across the furnace toward exhaust ports which carry away thecombustion products.

it is obviously desirable, therefore, to have a furnace which combinesthe advantages of both the recuperator and regenerator types ofpreheating combustion air. Attempts to obtain the most advantageousarrangement and in which a plurality of recuperators have been utilizedare illustrated in the prior art in U.S. Pat. No. l,864,087, issued June21, 1932, and U.S. Pat. No. 2,004,916, issued June 11, 1935. While thestructures illustrated in the above referenced patents have contributedto the art, all the problems associated with the attempt to gain theadvantages of both recuperative and regenerative type of heat exchangehave not beensolved.

It is, therefore, an object of this invention to provide an improvedheating furnace.

It is a further object of this invention to provide an improved heatingfurnace utilizing a plurality of recuperator units for heat exchangebetween hot flue gases and combustion air to be supplied to burners inthe furnace.

ln carrying out the above objects, the invention features in a preferredembodiment a tank-type glass-melting furnace wherein the furnaceincludes sidewalls, end walls, a top wall and a bottom wall defining achannel in which batch materials are melted to form a stream of moltenglass that flows from a batch charge area in one end wall to a moltenglass discharge area in the other end wall. A plurality of burnerstations are spaced along one of the sidewalls. Exhaust port means foreach burner station is formed in the one sidewall above its associatedburner station and aligned therewith whereby a flow pattern forsubstantially all of combustion products from each burner station isestablished out in a first current over the glass in the heatingchamber, and up and back over the first current in a second current tothe exhaust port means in the sidewall above that burner station.Recuperator means are provided for each exhaust port means and include afirst chamber for receiving combustion products from the exhaust portmeans and a second chamber in heat exchange relationship with the firstchamber for preheating combustion air for the burner stations.

A common header may be connected to the second chambers of therecuperator means for supplying preheated combustion air to the burnerstations. The common header is advantageously connected to supplycombustion air to a burner station, substantially all of which air hasbeen preheated by exhaust combustion products from that burner stationto correlate the temperature of the preheated combustion air with theamount of heat desired to be supplied to the furnace by that burnerstation.

A preferred embodiment also includes a second plurality of burnerstations spaced along the other of the sidewalls. Exhaust port means foreach of the second plurality of burner stations are formed in the othersidewall above its associate burner station and again aligned therewith,wherewith a flow pattern for substantially all the combustion productsfrom each of the second plurality of burner stations is established froma burner station out in a first current over the glass in the heatingchamber and up and back over the first current in the second current tothe exhaust port means in the sidewall above that burner station.Recuperator means are also provided for each of the exhaust port meansfor the second plurality of burner stations, each including a firstchamber for receiving combustion products from an exhaust port means anda second chamber in heat exchange relationship with said first chamberfor preheating combustion air for the burner stations.

Each of the first-mentioned plurality of burner stations isadvantageously paired with and positioned substantially directly acrossfrom one of the second plurality of burner stations so that the flowpatterns from each pair of burner stations define a heating zone acrossthe channel. Control means are provided for each burner station forregulating the temperature of each of the zones.

Means are also disclosed and described for selectively blocking flow ofcombustion products and combustion air through each recuperator means toenable repair or maintenance thereof without shutting down the furnace.

Other objects, advantages and features of this invention will becomeapparent from the following description when taken in conjunction withthe accompanying drawings, in which:

FIG. 1 is a plan view of a heating furnace embodying the teachings ofthis invention; and

FIG. 2 is an enlarged cross-sectional view of the apparatus illustratedin FIG. 1 taken along lines 11-11,

Referring to the drawings there is illustrated a tank-type glass-meltingfurnace designated generally at which includes sidewalls 13, 14; endwalls 11, 12; a top wall 15 and a bottom wall 16 defining a channel 17in which batch materials are melted to form a stream of molten glassthat flows from a batch charge area 18 in one end wall to a molten glassdischarge area 19 in the other end wall.

A plurality of burner stations are spaced along sidewall 13. Exhaustport means for each burner station 30 is formed in the sidewall 13 aboveits associated burner station and aligned therewith whereby a flowpattern (best seen in FIGv 2) for substantially all of the combustionproducts from a burner station 30 is established in a first current outover the glass 20 in the heating chamber and up and back over the firstcurrent 50 in a second current 51 to the associated exhaust port 40 inthe sidewall 13 above a burner station 30.

A burner station may include one or more burner nozzles. Exhaust portmeans 40 may include one or more ports formed in the sidewall 13.However, the burner stations and exhaust ports must cooperate to providethe flow pattern as set forth hereinbefore.

A recuperator means generally indicated at 60 is provided for eachexhaust port 40 and includes a first chamber 61 for receiving combustionproducts from the exhaust port 40 and a second chamber 62 in heatexchange relationship with the first chamber 61 for preheatingcombustion air for the burner stations 30.

Combustion air is provided for preheating from a supply 79 and is routedvia a common header 80 through individual valves 82 and conduits 83 tothe chamber 62. After being heated the combustion air exits from chamber62 via individual conduit 93 and valve 92 to a common header 90.Preheated combustion air from the common header 90 is supplied viaindividual conduits 94 to a burner control 100 for each burner station30. Fuel from a fuel supply 99 is also provided to the burner control100 to be mixed in the ratio desired with the preheated combustion air.

The common header 90 is connected to the second chamber 62 of all of therecuperators 60. The common header 90 is advantageouslyconnected tosupply combustion air to a burner station, substantially all of whichair has been preheated by exhaust combustion products from that burnerstation to correlate the temperature of the preheated combustion airwith the amount of heat desired to be supplied to the furnace by thatburner station. This is accomplished by placing an inlet 93 to header 90closely adjacent to a supply conduit 94 from header 90 for an associatedburner station-exhaust port combination.

The furnace illustrated in the drawings further includes a secondplurality of burner stations 31 spaced along the other sidewall 14.Exhaust port means 41 for each of the second plurality of burnerstations 31 is formed in the other sidewall 14 above its associatedburner station and aligned therewith whereby a flow pattern forsubstantially all of the combustion products from each of the secondplurality of burner stations 31 is established out in a first currentover the glass 20 in the heating chamber, and up and back over the firstcurrent 55 in a second current 56 to the exhaust port means 41 in thesidewall 14 above a burner station 31. Recuperator means are providedfor each of the exhaust ports 41 for each of the second plurality ofburner stations 31 which are substantially identical to the recuperatorstations generally indicated at 60. Combustion air is routed from an airsupply 79 via a common header 81 to the recuperators. After thecombustion air is heated it is directed through a common header 91 tothe individual burner stations in the same manner as illustrated anddescribed hereinbefore for the burner stations on the other side of thefurnace.

The exhaust combustion products from ports 40 and 41, after travelingthrough chamber 61 of recuperator 60, is directed via common header orcanals such as indicated at 70 which may be formed in refractory such asillustrated at 71 and 72 to a common stack 73.

Each of the first-mentioned plurality of burner stations 30 isadvantageously paired with and positioned substantially directly acrossfrom one of the second plurality of burner stations 31 so that the flowpatterns from each pair of burner stations defines a heating zone acrossthe channel 17. The burner control means 100 for each of the pair ofburner stations 30, 31 may thus be utilized for regulating thetemperature and the pressure in each of the zones established by theflow patterns.

Referring to FIG. 2 there is illustrated means for selectively blockingflow of exhaust combustion products and combustion air through each ofthe recuperator means to enable repair or maintenance thereof withoutshutting down a furnace. A first gate or valve means 75 is provided toblock flow from an exhaust port 40 into a recuperator. A second gate orvalve means 76 is provided to block backflow from the common exhaustcanal 70 back up into a recuperator 60 which is being repaired. Thevalve 82 may be utilized to block flow from the common header ofcombustion air to be preheated while the valve 92 may be utilized toblock the backflow from the common header which is supplying preheatedcombustion air to the burner controls 100.

By blocking off an individual recuperator means as described abovefurnace operation may continue, since combustion air is being suppliedfrom the common header 90 to all burner controls and since thecombustion products from the burner station will be temporarily divertedto other exhaust port means. Thus an additional recuperator may berepaired or replaced without shutting down the operation of the furnace.

By installing a plurality of smaller recuperators in each of the exhaustports of the furnace the required volume of combustion air for a largefurnace may be provided. Thus the necessity for huge recuperators isavoided while obtaining the advantages of the recuperator. Further, byhaving a plurality of smaller recuperators to accept the required volumeof combustion air the heat exchange surfaces available for preheatingthe combustion air are increased by a factor of three, in the apparatusillustrated, to enable a more efficient heat exchange. Still further,since the recuperators are installed closely adjacent the furnace, thetemperature of the combustion products is higher and so an additionalefficiency is obtained.

As noted before, there is an increased ability to control temperatureand pressure within a designated zone because of the flow patterns thathave been established by the structure described.

In the past exhaust combustion gases have flowed over the full length ofthe furnace to one or two larger exhaust ports. This tended to pick upthe dust and finer particles from the batch material that is beingcharged at area 18, carrying the batch materials out the stack with theexhaust gases. With the present system each exhaust port combines with aburner station to set up a zone flow. Thus only the first few zoneswould be exposed to batch, the remainder of the zones being over glassthat is already melted. In addition, since the flow patterns establishedby the current 50, 55 and 51, 56 meet substantially in the middle of thefurnace and go upwardly and backwardly the batch that may be picked upis generally dropped out of the current when the flow pattern reversesdirection.

It is desirable to have a hotspot zone to restrict batch flow fromfloating on top of the pool of molten glass toward the discharge end 19of the furnace. As noted hereinbefore the temperatures of each of thezones may be selectively regulated because of the flow patterns thathave been established, thus enabling the furnace to have a hotspot zonewherever desired.

Since the flame patterns are individual the batch pickup or batchcarryover is reduced, thereby keeping an advantage of a regenerativefurnace while gaining the advantage of a recuperator. The flow patternsdescribed enable the establishment of a more uniform overall pressureand temperature gradient in the furnace. This avoids the pressuregradient across the furnace in a regenerator. Better stability isprovided since each recuperator is smaller and thus provides bettercontrol for each zone. In addition, since the flow of the flame goes outover the glass and then doubles back above itself, it insulates therefractory of the crown or roof from the direct heat of the flame.Although the invention is particularly applicable to larger furnaces,the better control provided by the flow patterns described make ituseful in small furnaces as well.

The invention hereinbefore described also enables conversion of aregenerator-type furnace to a recuperator-type furnace as shown, with aminimum of construction change in the furnace itself, The melting tankand ports of the regenerator furnace would remain undisturbed. Theregenerators would be dismantled down to the rider arch and canal forexhaust gases. A recuperator would then be installed to connect theports to the canal. The burners would be installed in the walls of thefurnace below the ports. Thus the existing brickwork would be leftundisturbed except for the removal of the regenerators and theinstallation of the recuperators would provide a substantial spacesaving.

It should be noted that although the exhaust port means 40, 41 are shownformed in the sidewalls 13, 14, respectively, of the furnace it ispossible to obtain substantially the same flow patterns shown in FIG. 2by forming the exhaust ports in the roof but closely adjacent thesidewalls 13, 14.

In conclusion, it is pointed out that while the illustrated exampleconstitutes a practical embodiment of the invention, it is not intendedto limit the invention to the exact details shown since modificationsmay be made without departing from the spirit and scope of the inventiondisclosed.

lclairn:

l. A furnace including sidewalls, end walls, a top wall and a bottomwall defining a heating chamber in which material to be heated enterssaid heating chamber through one of said end walls and exits through theother of said end walls; a plurality of burner stations spaced along oneof said sidewalls; exhaust port means for each burner station formed ina wall above its associated burner stations whereby a flow pattern forsubstantially all of the combustion products from each burner station isestablished from each burner station out in a first current overmaterial in said heating chamber and up and back over said first currentto the exhaust port means above that burner station; and recuperatormeans for each exhaust port means for passing combustion products fromsaid exhaust port means in heat exchange relationship with combustionair for said burner stations.

2. Apparatus as defined in claim 1 which further includes a commonheader connected to all of said recuperator means for supplyingpreheated combustion air to said burner stations.

3. Apparatus as defined in claim 1 which further includes a secondplurality of burner stations spaced along the other of said sidewalls;exhaust port means for each of said second plurality of burner stationsformed in a wall above its associated burner station whereby a flowpattern for substantially all of the combustion products from each ofthe second plurality of burner stations is established from a burnerstation out in a first current over material in said heating chamber andup and back over said first current to the associated exhaust portmeans; and recuperator means for each of said exhaust port means foreach of said second plurality of burner stations for passing combustionproducts from said exhaust port means in heat exchange relationship withcombustion air for said burner stations.

4. Apparatus as defined in claim 3 which further includes a first commonheader connected to all of said recuperator means on one side of saidfurnace for supplying preheated combustion air to burner stations onsaid one side, and a second common header connected to all of saidrecuperator means on the other side of said furnace for supplyingpreheated combustion air to burner stations on said other side.

5. Apparatus as defined in claim 3 in which each of the firstmentionedplurality of burner stations is aligned with one of said secondplurality of burner stations across the heating chamber.

6. In a tank-type glass-melting furnace wherein said furnace includessidewalls, end walls, a top wall and a bottom wall defining a channel inwhich batch materials are melted to form a stream of molten glass thatflows from a batch charge area in one end wall to a molten glassdischarge area in the other end wall; a plurality of burner stationsspaced along one of said sidewalls; exhaust port means for each burnerstation formed in said one sidewall above its associated burner stationand aligned therewith whereby a flow pattern for substantially all ofthe combustion products from each burner station is established out in afirst current over the glass in the heating chamber and up and back overthe first current in a second current to the exhaust port means in thesidewall above that burner station; and recuperator means for eachexhaust port means including a first chamber for receiving combustionproducts from an exhaust port means and a second chamber in heatexchange relationship with said first chamber for preheating combustionair for said burner stations.

7. Apparatus as defined in claim 6 which further includes a commonheader connected to said second chambers of said recuperator means forsupplying preheated combustion air to said burner stations.

8. Apparatus as defined in claim 7 in which said common header isconnected to supply combustion air to a burner station, substantiallyall of which has been preheated by exhaust combustion products from thatburner station to correlate the temperature of the preheated combustionair with the amount of heat desired to be supplied to the furnace bythat burner station.

9. Apparatus as defined in claim 6 which further includes a secondplurality of burner stations spaced along the other of said sidewalls;exhaust port means for each of said second plurality of burner stationsformed in said other side wall above its associated burner station andaligned therewith whereby a flow pattern for substantially all of thecombustion products from each of said second plurality of burnerstations is established from a burner station out in a first currentover the glass in the heating chamber and up and back over the firstcurrent in a second current to the exhaust port means in the sidewallabove that burner station; and recuperator means for each of saidexhaust port means for each of said second plurality of burner stationsincluding a first chamber for receiving combustion products from anexhaust port means and a second chamber in heat exchange relationshipwith said first chamber for preheating combustion air for said burnerstations.

10. Apparatus as defined in claim 9 which further includes a firstcommon header connected to receive preheated combustion air from all ofsaid recuperator means on one side of said furnace and supply combustionair to burner stations on said one side; and a second common headerconnected to receive preheated combustion air from all of saidrecuperator means on the other side of said furnace and supplycombustion air to burner stations on said other side; each common headerbeing connected to circulate combustion air to a burner station whichhas received substantially all of its preheat from a heat exchange withexhaust combustion products from the same burner station.

11. Apparatus as defined in claim 9 in which each of the first-mentionedplurality of burner stations is paired with and positioned substantiallydirectly across from one of aid second plurality of burner stations sothat the flow patterns from each pair of burner stations define aheating zone across said channel.

12. Apparatus as defined in claim 11 which further includes controlmeans for each burner station for regulating the temperature of each ofsaid zones.

13. Apparatus as defined in claim 9 which further includes means forselectively blocking flow of exhaust combustion products and combustionair through each recuperator means to enable repair or maintenancethereof without shutting down the furnace.

14. A firing system adaptable for use with a furnace which requires aplurality of burners comprising a. a burner station for dispositionthrough a wall of a furnace,

b. individual recuperator means for said burner station, and

c. exhaust port conduit means having a combustion products receiving enddisposed above said burner station for conducting combustion productsfrom that burner station to the individual recuperator means for thatburner station,

d. said combustion products receiving end of said conduit means beingaligned with its associated burner station whereby a flow pattern forsubstantially all of the combustion products from the associated burnerstation is established out in a first current from the burner stationand up and back over the first current in a second current to saidconduit means.

15. A firing system adaptable for use with a furnace which requires aplurality of burners comprising,

a. a plurality of aligned burner stations for disposition along andthrough one wall ofa furnace,

b. individual recuperator means for each of said burner stations, and

c. exhaust port conduit means for each of said plurality of burnerstations for conducting combustion products from its associated burnerstation to the recuperator means individual to that station,

d. each exhaust port conduit means having a combustion has opposingwalls and requires a plurality of burners comprising,

a. a pair of opposed burner stations for disposition through opposingwalls ofa furnace,

b. individual recuperator' means for each of said burner stations, and

. exhaust port conduit means for each of said plurality of burnerstations for conducting combustion products from its associatedburnerstation to the recuperator means individual to that station,

d. each exhaust port conduit means having a combustion productsreceiving end disposed above and aligned with its associated burnerstation whereby a flow pattern for substantially all of the combustionproducts from its associated burner station is established out in afirst current from the burner station and up and back over the firstcurrent in a second current to said conduit means.

1. A furnace including sidewalls, end walls, a top wall and a bottomwall defining a heating chamber in which material to be heated enterssaid heating chamber through one of said end walls and exiTs through theother of said end walls; a plurality of burner stations spaced along oneof said sidewalls; exhaust port means for each burner station formed ina wall above its associated burner stations whereby a flow pattern forsubstantially all of the combustion products from each burner station isestablished from each burner station out in a first current overmaterial in said heating chamber and up and back over said first currentto the exhaust port means above that burner station; and recuperatormeans for each exhaust port means for passing combustion products fromsaid exhaust port means in heat exchange relationship with combustionair for said burner stations.
 2. Apparatus as defined in claim 1 whichfurther includes a common header connected to all of said recuperatormeans for supplying preheated combustion air to said burner stations. 3.Apparatus as defined in claim 1 which further includes a secondplurality of burner stations spaced along the other of said sidewalls;exhaust port means for each of said second plurality of burner stationsformed in a wall above its associated burner station whereby a flowpattern for substantially all of the combustion products from each ofthe second plurality of burner stations is established from a burnerstation out in a first current over material in said heating chamber andup and back over said first current to the associated exhaust portmeans; and recuperator means for each of said exhaust port means foreach of said second plurality of burner stations for passing combustionproducts from said exhaust port means in heat exchange relationship withcombustion air for said burner stations.
 4. Apparatus as defined inclaim 3 which further includes a first common header connected to all ofsaid recuperator means on one side of said furnace for supplyingpreheated combustion air to burner stations on said one side, and asecond common header connected to all of said recuperator means on theother side of said furnace for supplying preheated combustion air toburner stations on said other side.
 5. Apparatus as defined in claim 3in which each of the first-mentioned plurality of burner stations isaligned with one of said second plurality of burner stations across theheating chamber.
 6. In a tank-type glass-melting furnace wherein saidfurnace includes sidewalls, end walls, a top wall and a bottom walldefining a channel in which batch materials are melted to form a streamof molten glass that flows from a batch charge area in one end wall to amolten glass discharge area in the other end wall; a plurality of burnerstations spaced along one of said sidewalls; exhaust port means for eachburner station formed in said one sidewall above its associated burnerstation and aligned therewith whereby a flow pattern for substantiallyall of the combustion products from each burner station is establishedout in a first current over the glass in the heating chamber and up andback over the first current in a second current to the exhaust portmeans in the sidewall above that burner station; and recuperator meansfor each exhaust port means including a first chamber for receivingcombustion products from an exhaust port means and a second chamber inheat exchange relationship with said first chamber for preheatingcombustion air for said burner stations.
 7. Apparatus as defined inclaim 6 which further includes a common header connected to said secondchambers of said recuperator means for supplying preheated combustionair to said burner stations.
 8. Apparatus as defined in claim 7 in whichsaid common header is connected to supply combustion air to a burnerstation, substantially all of which has been preheated by exhaustcombustion products from that burner station to correlate thetemperature of the preheated combustion air with the amount of heatdesired to be supplied to the furnace by that burner station. 9.Apparatus as defined in claim 6 which further includes a secondplurality of burner stations sPaced along the other of said sidewalls;exhaust port means for each of said second plurality of burner stationsformed in said other side wall above its associated burner station andaligned therewith whereby a flow pattern for substantially all of thecombustion products from each of said second plurality of burnerstations is established from a burner station out in a first currentover the glass in the heating chamber and up and back over the firstcurrent in a second current to the exhaust port means in the sidewallabove that burner station; and recuperator means for each of saidexhaust port means for each of said second plurality of burner stationsincluding a first chamber for receiving combustion products from anexhaust port means and a second chamber in heat exchange relationshipwith said first chamber for preheating combustion air for said burnerstations.
 10. Apparatus as defined in claim 9 which further includes afirst common header connected to receive preheated combustion air fromall of said recuperator means on one side of said furnace and supplycombustion air to burner stations on said one side; and a second commonheader connected to receive preheated combustion air from all of saidrecuperator means on the other side of said furnace and supplycombustion air to burner stations on said other side; each common headerbeing connected to circulate combustion air to a burner station whichhas received substantially all of its preheat from a heat exchange withexhaust combustion products from the same burner station.
 11. Apparatusas defined in claim 9 in which each of the first-mentioned plurality ofburner stations is paired with and positioned substantially directlyacross from one of aid second plurality of burner stations so that theflow patterns from each pair of burner stations define a heating zoneacross said channel.
 12. Apparatus as defined in claim 11 which furtherincludes control means for each burner station for regulating thetemperature of each of said zones.
 13. Apparatus as defined in claim 9which further includes means for selectively blocking flow of exhaustcombustion products and combustion air through each recuperator means toenable repair or maintenance thereof without shutting down the furnace.14. A firing system adaptable for use with a furnace which requires aplurality of burners comprising a. a burner station for dispositionthrough a wall of a furnace, b. individual recuperator means for saidburner station, and c. exhaust port conduit means having a combustionproducts receiving end disposed above said burner station for conductingcombustion products from that burner station to the individualrecuperator means for that burner station, d. said combustion productsreceiving end of said conduit means being aligned with its associatedburner station whereby a flow pattern for substantially all of thecombustion products from the associated burner station is establishedout in a first current from the burner station and up and back over thefirst current in a second current to said conduit means.
 15. A firingsystem adaptable for use with a furnace which requires a plurality ofburners comprising, a. a plurality of aligned burner stations fordisposition along and through one wall of a furnace, b. individualrecuperator means for each of said burner stations, and c. exhaust portconduit means for each of said plurality of burner stations forconducting combustion products from its associated burner station to therecuperator means individual to that station, d. each exhaust portconduit means having a combustion products receiving end disposed aboveand aligned with its associate burner station whereby a flow pattern forsubstantially all of the combustion products from its associated burnerstation is established out in a first current from the burner stationand up and back over the first current in a second current to saidconduit means.
 16. A firiNg system adaptable for use with a furnacewhich has opposing walls and requires a plurality of burners comprising,a. a pair of opposed burner stations for disposition through opposingwalls of a furnace, b. individual recuperator means for each of saidburner stations, and c. exhaust port conduit means for each of saidplurality of burner stations for conducting combustion products from itsassociated burner station to the recuperator means individual to thatstation, d. each exhaust port conduit means having a combustion productsreceiving end disposed above and aligned with its associated burnerstation whereby a flow pattern for substantially all of the combustionproducts from its associated burner station is established out in afirst current from the burner station and up and back over the firstcurrent in a second current to said conduit means.